How can I modify the default behaviour of Ubuntu 12.04 (& 12.10) to prevent a symbolic link from /dev/shm to /run/shm ever being created on boot up?

Question

Whilst installing Oracle 11gR2 Express Edition on Ubuntu 12.04 by following the Oracle 11gR2 Express Edition on Linux Ubuntu 11.10 howto and have encountered the Oracle memory target problem with /dev/shm (as documented in section 7. of that guide) since /dev/shm is now implemented by default as a symbolic link as noted in the Ubuntu 11.10 release notes from /dev/shm to /run/shm. The symbolic link is incompatible with what Oracle expects and this results in an Oracle error (ORA-00845: MEMORY_TARGET) on database startup.

Section 7) of the 'Oracle 11gR2 Express Edition on Linux Ubuntu 11.10 howto' documents a startup script /etc/init.d/oracle-shm that is meant to configure /dev/shm to use Ubuntu’s /run/shm, however this does not appear to have the desired effect on Ubuntu 12.04 and /dev/shm is not mounted as expected - presumably it did work on 11.10. Although this has already been noted and various solutions proposed I chose to work around the problem in a slightly different way by adding an entry to /etc/fstab and modifying the /etc/init.d/oracle-shm script as follows:

1. Adding an entry for the shared memory temporary file system to /etc/fstab, say (for a 2 gigabyte file)

   shm /dev/shm    tmpfs   size=2g 0   0
   

2. Changing the mount line in /etc/init.d/oracle-shm from:

   rm -f /dev/shm  
   mkdir /dev/shm
   mount -B /run/shm /dev/shm
   

   to simply

   rm -f /dev/shm
   mkdir /dev/shm 
   mount /dev/shm
   

Regardless, all the proposed solutions involve undoing the default Ubuntu behaviour at bootup, by first removing the symbolic link and then implementing the desired behaviour.

I would like to be able to setup the shared memory file system once and for all by:

1. Adding an entry for the shared memory temporary file system to /etc/fstab, say (for a 2 gigabyte file)

   shm /dev/shm    tmpfs   size=2g 0   0
   

2. Remove the existing symbolic link to /dev/shm and create as a directory, as sudo.

   rm –f /dev/shm
   mkdir /dev/shm
   

3. Mounting the shared memory temporary file system

   mount /dev/shm
   

This all works fine until you reboot, at which point the symbolic link from /dev/shm to /run/shm re-appears instead of /dev/shm being mounted as a shared memory temporary file system.

Here’s the question then.

How can I modify the default behaviour of Ubuntu 12.04 (& 12.10) to prevent a symbolic link from /dev/shm to /run/shm ever being created in the first place on boot up?

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Answer 1

In /etc/init/mounted-dev.conf remove the line

 [ -e /dev/shm ] || ln -s /run/shm /dev/shm